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Discussion Starter · #1 · (Edited)
Since I purchased my cruze this a project I have wanted to take on. Over the past month I have been making and fitting templates and finally welded up a prototype. Several years ago I had an 04 GTO and installed a diffuser from difflow.com, pics of my car still on their site (red one) also a good source to look at if you are unfamiliar with the purpose of this. It felt like someone had taken a bag of bricks out of the trunk, and I got 2 more mpgs. Upon some investigation I could not find anyone who made something for our cars, so it was up to me.
I have a picture of my first aluminum template, I finally made this after several cardboard tries. Regardless of the exhaust cut out it still concerned me, as well as the weight. Once I had the nice ridged piece under there it became clear that covering the entire under bumper was out of the question. I opted to go with a more conventional design. The finished product is 1/8th" aluminum sheet with the fins and tabs tig welded on. The front mounts are a 3" rubber pipe coupler cut down to the size of the galvanized duck hanger. I didn't want it rubbing away at the sub frame so the rubber from the pipe should protect that, as well as offer a spongy surface to tight against. Two 1/4 X 20 1" bolts with washers hold everything tight. Once tightened down The strap tensioned up nicely, It's not going anywhere. This prototype gives me chance to see the effect I'm having before I take to much making a final version, as well check fitment. I was in a hurry and welded everything in one night so the aluminum warped pretty bad. The final rendition will have to be welded over the course of a few nights. It will also sport three 3" tabs in the middle and two 1 1/2" tabs on the sides, also raised 1/4" instead of 1/8th (I had to bend them for proper fitment). For now the three smaller tabs should hold on fine for testing. I forgot to weigh it but I imagine it's adding 15-20lbs. The final version will have an exact weight.
So far I have only taken a 30 mile test drive. I travel that same way often and in similar conditions, despite the small distance I have noticed 3 more mpgs and smoother shifts due to less energy lost when clutching. So far I am extremely happy with the results. Tomorrow it will be going on a few hundred mile journey, I will report back with my more conclusive findings. As for the visual appeal I am very happy. The outside curve needs some more smoothing and I may make the fins slightly taller. Only once I have conclusive results as well my final version and templates made, I may offer to make some for interested members. I will also be working on a non RS model soon using a co-workers eco cruze. For those who might be interested in the future keep in mind all of this work is done by hand. I do not have access to a water jet or CNC. I use a plasma cutter, sanding belt, right angle sander, and tig welder. Aluminum is not easy to weld, especially this thin, so there could be minor warping, bulging on the other side, or other imperfections. All of that is a long way away, and admins, I would be getting with you if that day comes.
Upon seeing the bare aluminum under there the my thoughts changed. I almost wouldn't mind a polished look rather than the black I was picturing. To paint it, you must be very very clean, and use a special etching primer so doing it for the prototype as unreasonable. I am trying to make smart power with my little build on this car, while maintaining a clean factory look, only modified to the trained eye. If I do produce these, and you would want something different, it could be done but increase the steep price I'd be asking. Building once of these takes several hours and a lot of patient machining, measuring, and clamping.
But enough of all that, onto what your hear to see. I will keep up this thread with my findings as well as progress on the finished product. I hope for +5 mpgs when it's done. And since my cruze will never see the strip, I would make a sweet deal to someone willing to run some time trials with and w/o the diffuser on the track. I would expect a second off the 1/4 mile. Land vehicle Vehicle Car Bumper Automotive exterior Car Vehicle Bumper Automotive exterior Red Car Vehicle Automotive lighting Vehicle registration plate Full-size car Bumper Auto part Automotive exterior Auto part Metal Auto part Automotive exterior Bumper Hood Auto part Edit: Better picture to come, I'll get them in order next time
 

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Discussion Starter · #2 ·
220 miles trip today. With the small numbers and temperature change it's difficult to say 100%. Regardless, I noticed a 2-3 mpg increase.
 

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Adding the ECO under panels will improve airflow as well.
 
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Which panels do you speak of? I am unfamiliar with the ecos for the most part.


Been driving more consistently recently. mileage increase seems to be settling out around +2.3 mpgs.
 

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Since I purchased my cruze this a project I have wanted to take on. Over the past month I have been making and fitting templates and finally welded up a prototype. Several years ago I had an 04 GTO and installed a diffuser from difflow.com, //edit//
Do you remember what the Difflow diffuser was made from?
 

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I believe these are only a salvage yard find. If they don't damage them.
yeah I managed to damage mine getting stuck in ice. I have pics but photobucket doesn't like me today. The panels are under the seats and just before the rear suspension under the gas tank.
 

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Discussion Starter · #9 ·
Do you remember what the Difflow diffuser was made from?
Theirs was 16th" aluminum. However the fins were bent over 90 degrees and riveted on. I wanted to weld mine so I opted for the thicker material.

yeah I managed to damage mine getting stuck in ice. I have pics but photobucket doesn't like me today. The panels are under the seats and just before the rear suspension under the gas tank.
Alright, Thanks for the info. I will look under my co-worker eco today and see if I cant get a better idea for them. From the picture it doesn't look like the RS skirts will matter. I'm wondering if the mounting will be available or if drilling will be needed.
 
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